Fiber optic cable protection in a mining system

ABSTRACT

A chain link assembly, a cable chain assembly and a mining system. The cable handler individual links may include an enclosed section for the fiber optic cable separate from other services for the machine. A flexible material or other structure may assemble the fiber optic cable in the cable handler in a manner in which it “snakes” about the centerline to provide ample slack in the fiber optic cable to, for example, prevent over tension.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of prior-filed, co-pending U.S.application Ser. No. 13/013,627, filed Jan. 25, 2011, the entirecontents of which are incorporated herein by reference.

FIELD

The present invention relates to longwall mining and, more particularly,to a cable handler chain in a longwall mining installation.

SUMMARY

A longwall shearer traverses along an armoured face conveyor (AFC) panline to win material from the face. The operation of the shearerrequires electrical power for cutting and tramming as well as water forcooling machine components including electric motors and gearcases.These services are provided out-bye the longwall face and must travelalong the AFC to reach the shearer. Typically, these services laystatically along the AFC until the mid point of the face where theservices typically enter the cable handling system which runs in atrough to the shearer towing bracket. The towing bracket is attached tothe shearer and pulls the cable handler, with services inside, along thetrough. The cable handling system is designed to withstand tensioncaused from the weight of the system and friction as it is being toweddown the cable trough, protecting the services which are not designed towithstand these forces.

The services provided to the shearer typically include only electriccables and water hoses. However, fiber optics is becoming increasinglyappealing as a way to, for example, provide an unmanned face in low seamlongwall mining installations or even in high seam mining. Fiber opticcores are used for high speed single- and two-way communication betweenthe shearer and the off-face equipment. The information consists ofsystem I/O, diagnostic information, radio control and videotransmission. If fiber optic cables are used for such communications,reliability of the fiber optic cores is important. The maximum tensionalload for the fiber optic cores is considerably lower than all othercables being routed to the shearer.

The illustrated constructions may provide a reliable means oftransmitting the data by protecting the fiber optic cable from overtension and failure. Reliability is important as significant downtimeresults in lost production and revenues of the mine, and, because ofdifficult ergonomic conditions associated with low seam longwall mining,repairs are difficult.

In order to ensure the reliability of the fiber optic cable, the fiberoptic cable may be placed in a separate compartment within the cablechain. This separate compartment may be formed by adding a divider tothe chain link to create two different compartments, one for theelectrical power cable/water hose and a much smaller one for the fiberoptic cable. A compressible material may provide a means to assemble thefiber cable in such a way to ensure adequate slack exists over theentire length of the cable chain to prevent over tension and failure.

The separate compartment may ensure that the other larger lines cannotdamage the fiber optic cable by sliding up against and over tensioningand wearing the fiber cable due to friction. The separate compartmentmay also provide means of constraining the compressible material in alldegrees of freedom.

In one independent embodiment, a chain link assembly may generallyinclude a chain link having a plurality of walls cooperating to define acompartment opening in the direction of the axis, a fiber optic cablebeing supportable in the compartment, a service line (e.g., a powercable, a water hose, etc.) being supportable in the compartment, and aflexible member supported in the compartment and engageable with thefiber optic cable, the flexible member positioning the fiber optic cabletoward one of the plurality of walls.

In some constructions, the flexible member may include a compressiblemember supported on an opposite one of the plurality of walls. Thecompressible member may include a substantially solid member formed ofcompressible material. The compressible member may include a hollowmember having a first portion engageable with the fiber optic cable anda second portion spaced from the first portion and engaging the oppositeone of the plurality of walls. The hollow member may have asubstantially tubular cross section. The compressible member may includea leaf spring. In some constructions, the flexible member may beconnected to the one of the plurality of walls and extends at leastpartially around the fiber optic cable, the flexible member being intension towards the one of the plurality of walls.

In some constructions, the chain link may further include an internalwall dividing the compartment into a first compartment and a secondcompartment, the fiber optic cable being supportable in the firstcompartment, the service line being supportable in the secondcompartment. The internal wall may extend between the one of theplurality of walls and an opposite one of the plurality of walls todefine the first compartment on one side of the internal wall and thesecond compartment on the other side of the wall. The internal walls maybe formed with the one of the plurality of walls and an opposite one ofthe plurality of walls.

The internal wall may be separate from and connected to the one of theplurality of walls and an opposite one of the plurality of walls. One ofthe plurality of walls may define a first groove, and the opposite oneof the plurality of walls may define a second groove. The internal wallmay include a first projection engageable in the first groove and asecond projection engageable in the second groove to connect theinternal wall to the one of the plurality of walls and to the oppositeone of the plurality of walls. The internal wall may include aconnecting member, a portion of the flexible member being capturedbetween the connecting member and an opposite one of the pluralitywalls.

The flexible member may have a surface engageable with the fiber opticcable, the surface including a low friction material. The surface may becoated with the low friction material. The flexible member may have asurface engageable with the fiber optic cable, the surface having curvededges.

In another independent aspect, a cable chain assembly may generallyinclude a plurality of chain links each having a top wall, a bottomwall, a first side wall and a second side wall cooperating to define acompartment opening in the direction of the axis, a fiber optic cableextending through the compartment in each of the plurality of chainlinks, the fiber optic cable extending generally along a wave-shapedpath, a service line supportable in the compartment in each of theplurality of chain links, a first flexible member supported in thecompartment of one of the plurality of chain links and engageable withthe fiber optic cable, the first flexible member positioning the fiberoptic cable toward the top wall of the one of the plurality of chainlinks, and a second flexible member supported in the compartment asecond one of the plurality of chain links and engageable with the fiberoptic cable, the second flexible member positioning the fiber opticcable toward the bottom wall of the second one of the plurality of chainlinks.

In some constructions, a third one of the plurality of chain links maybe connected between the one of the plurality of chain links and thesecond one of the plurality of chain links, the third one of theplurality of chain links not having a flexible member in thecompartment. Each of the plurality of chain links may include a pair offorward projections and a pair of rearward projections each defining anopening, and the assembly may further include a first pin connecting therearward projections of the one of the plurality of chain links to theforward projections of the third one of the plurality of chain links,the first pin defining a pivot axis between the one of the plurality ofchain links and the third one of the plurality of chain links and asecond pin connecting the rearward projections of the third one of theplurality of chain links to the forward projections of the second one ofthe plurality of chain links, the second pin defining a pivot axisbetween the third one of the plurality of chain links and the second oneof the plurality of chain links.

In yet another independent embodiment, a mining system may generallyinclude an armoured face conveyor extending along a face to be mined,the conveyor defining a cable trough, a shearer supported by and formovement along the conveyor, the shearer being operable to mine materialfrom the face, and a cable chain assembly extending along an axisgenerally parallel to the face, the assembly being partially supportedin the trough. The assembly may include a plurality of chain links eachhaving a top wall, a bottom wall, a first side wall and a second sidewall cooperating to define a compartment opening in the direction of theaxis, a fiber optic cable extending through the compartment in each ofthe plurality of chain links, the fiber optic cable extending generallyalong a wave-shaped path, the fiber optic cable being connected to theshearer, a service line supportable in the compartment in each of theplurality of chain links, the service line being connected to theshearer, a first flexible member supported in the compartment of one ofthe plurality of chain links and engageable with the fiber optic cable,the first flexible member positioning the fiber optic cable toward thetop wall of the one of the plurality of chain links, and a secondflexible member supported in the compartment a second one of theplurality of chain links and engageable with the fiber optic cable, thesecond flexible member positioning the fiber optic cable toward thebottom wall of the second one of the plurality of chain links.

Independent aspects of the invention will become apparent byconsideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a longwall mining system including anArmoured Face Conveyor (“AFC”).

FIG. 2 is a top plan view of a portion of the longwall mining systemshown in FIG. 1 including the AFC, a shearer and a cable chain.

FIG. 3 is a profile view of a portion of the longwall mining systemshown in FIG. 1 including the AFC, the shearer and the cable chain.

FIG. 4 is a cross-sectional view of a portion of a cable chain of thelongwall mining system shown in FIG. 2.

FIG. 4A is a cross-sectional view of a portion of a cable chain of alongwall mining system according to another embodiment.

FIG. 4B is a cross-sectional view of a portion of a cable chain of alongwall mining system according to another embodiment.

FIG. 5 is a perspective cross-sectional view of a portion of the cablechain shown in FIG. 4.

FIG. 6 is a side cross-sectional view of a portion of the cable chainshown in FIG. 4.

FIG. 7 is a perspective cross-sectional view of an alternativeconstruction of the cable chain shown in FIG. 4.

FIG. 8 is a perspective cross-sectional view of another alternativeconstruction of the cable chain shown in FIG. 4.

FIG. 9 is a perspective cross-sectional view of yet another alternativeconstruction of the cable chain shown in FIG. 4.

DETAILED DESCRIPTION

Before any independent embodiments or independent constructions of theinvention are explained in detail, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the following drawings. Theinvention is capable of other independent embodiments and of beingpracticed or of being carried out in various ways.

A longwall mining system 10 is illustrated in the FIGS. 1-3. The system10 may be used in mines having a low seam or a high seam. The system 10generally includes an Armoured Face Conveyor (AFC) 14 extending along aface F to be mined (e.g., a coal block). A shearer 18 is supported onand traverses on the pan line 22 (see FIG. 3) of the AFC 14 to winmaterial from the face F. Head and tail drives 26, 30 (see FIG. 1) movethe conveyor of the AFC 14 to convey mined material (e.g., coal). Thelength of this system 10 is typically around 1000 feet.

As shown in FIGS. 2-3, the AFC 14 includes a cable trough 30 extendingalong an axis A generally parallel to the face F. A cable chain 34 ispositioned in the cable trough 30 and extends generally along the axisA. As shown in FIG. 4, service lines (e.g., electrical power cables 38,42, water hose 46) and a fiber optic cable 50 are supported in the cablechain 34.

As shown in FIGS. 5-6, the cable chain 34 is formed from a plurality ofchain links 54 a, 54 b, 54 c . . . 54 n. Each chain link 54 generallyincludes (see FIGS. 4-5) a plurality of walls (e.g., a top wall 58, abottom wall 62 and opposite side walls 66, 70) defining a linkcompartment 74 opening in the direction of the axis A. Each chain link54 also includes (see FIGS. 5-6) a set of forward and rearwardprojections 78, 82, each defining an opening 86 for receiving a pin (notshown) to connect the chain links 54 into a chain (see FIGS. 5-6).

In the illustrated construction and in some independent aspects, eachchain link 54 also includes an internal divider wall 90 dividing thelink compartment 74 into a first compartment 94, for the fiber opticcable 50, and a second compartment 98, for the service lines (38, 42,46). Each compartment 94, 98 is generally rectangular with the firstcompartment 94 being relatively narrow in a horizontal direction (seeFIG. 4). In other constructions (not shown), the compartment(s) 94, 98may have a different shape (e.g., square, round, oval, etc.) and/orsize.

In the construction shown in FIGS. 4-6 and 9, the divider wall 90 isformed with the other walls (58, 62) of the chain link 54. In otherconstructions (see, for example, FIGS. 4B and 5-8), the divider wall 90is separate from the chain link 54 and connected to the top and bottomwalls 58, 62 by inter-engaging connecting members (FIG. 4B) such as, forexample, keying projection(s) and groove(s) on the divider wall 90 andon the walls 58, 62. The connecting members cooperate to retain thedivider wall 90 in position. In such constructions, the walls 58, 62,66, 70 of the chain link 54 may also be formed separately from oneanother and connected by inter-engaging connecting members with afriction fit, pinned, etc.

In the illustrated construction and in some independent aspects, in atleast some of the chain links 54, a flexible member 102 is provided inthe first compartment 94 and engages the fiber optic cable 50. Flexiblemembers 102 are arranged along the cable chain 34 to provide anon-linear (e.g., wave-shaped) path P for the fiber optic cable 50 suchthat there is slack in the fiber optic cable 50 (the length of the fiberoptic cable 50 in the cable chain 34 is greater than the length of thecable chain 34).

The flexible member 102 may support and locate the fiber optic cable 50in the first compartment 94. The surface 106 of the flexible member 102engaging the fiber optic cable 50 includes a low friction material(e.g., the flexible member 102 may be formed of low friction materialand/or the surface 106 may be coated with low friction material (e.g., aslippery coating)) to limit the coefficient of friction between theflexible member 102 and fiber optic cable 50 thereby limiting theextension of the fiber optic cable 50 along its axis as the fiber opticcable 50 is tensioned. Also, the surface 106 and the edges/corners 110of the flexible member 102 in the area of the fiber optic cable 50 aresufficiently curved/rounded to prevent damage to the fiber optic cable50 when relative motion occurs between the flexible member 102 and thefiber optic cable 50.

In some constructions (for example, in FIGS. 4-6, in FIG. 7 and in FIG.8), the flexible member 102 includes a compressible member such that,when the fiber optic cable 50 is pulled, compression is induced in theflexible member 102. Applying tension T on the fiber optic cable 50causes the fiber optic cable 50 to compress the compressible member 102in the direction of arrow D (see FIG. 6).

In the construction shown in FIGS. 4-6, the flexible member 102 includesa solid compressible member 102 a formed of, for example, foam. Thecompressible member 102 a generally occupies the majority of the firstcompartment 94 (e.g., the remainder of the first compartment notoccupied by the fiber optic cable 50). The compressible member 102 a isconstructed to position the fiber optic cable 50 toward one wall (e.g.,the top wall 58 of the chain link 54 a, the bottom wall 62 of the chainlink 54 c).

In other constructions (FIG. 4A), the compressible member 102 a may beconstructed to at least partially encompass the fiber optic cable 50.For example, the compressible member 102 a may also include a portion(FIG. 4A) between the fiber optic cable 50 and one or both of theadjacent side walls (70, 90) of the first compartment 94 and/or aportion (FIG. 4A) between the fiber optic cable 50 and the one wall(e.g., the top wall 58 of the chain link 54 a, the bottom wall 62 of thechain link 54 c) to at least partially fill space around the fiber opticcable 50 (see FIG. 4). In constructions in which the compressible member102 a at least partially encompasses the fiber optic cable 50, thecompressible member 102 a may also be sufficiently rigid such that adivider wall may not be provided to separate the fiber optic cable 50from the service lines (38, 42, 46).

The compressible member 102 a is positioned against the opposite wall(e.g., the bottom wall 62 of the chain link 54 a, the top wall 58 of thechain link 54 c). In the illustrated construction (see FIG. 6), thesurface of the opposite wall is curved to match the shape of theadjacent surface of the compressible member 102 a. However, in otherconstructions (not shown), the surface of the opposite wall may have adifferent shape (e.g., linear).

In other constructions, the flexible member 102 includes a hollowcompressible member, such as a hollow tubular member, that will allowthe fiber optic cable 50 to deflect inwardly when subject to tension. Asshown in FIG. 7, the flexible member 102 includes a hose section 102 b(a short length of rubber hose). In a similar construction (see FIG. 8),the flexible member 102 includes a leaf spring 102 c. The leaf spring102 c may be made of a number of materials to achieve the desiredstiffness.

In the illustrated construction (see FIGS. 7-8), the divider wall 90includes a connector 114 (e.g., a cantilevered protrusion), and the hosesection 102 b or the leaf spring 102 c is retained by the connector 114(e.g., between the connector 114 and the opposite wall (e.g., the bottomwall 62 of the chain link 54 a, the top wall 58 of the chain link 54c)).

In a further construction, the flexible member 102 includes a tensionmember, such as an elastic band 102 d. The band 102 d is connected tothe one wall (e.g., the top wall 58 of the chain link 54 a, the bottomwall 62 of the chain link 54 c) and extends around the fiber optic cable50. When the fiber optic cable 50 is tensioned, taking up the slack, theband 102 d will be pulled in tension as well.

The band 102 d can be an open loop for easy assembly/disassembly and befastened to the wall 58 or 62 of the chain link 54. The walls 58, 62 areprovided with recessed connecting portions 118 such that the band 102 dis within the outer periphery of the chain link 54 (e.g., below the topwall 58 of the chain link 54 a, above the bottom wall 62 of the chainlink 54 c). Connecting the band 102 d below flush on the outer surfaceof the wall 58 or 62 may protect the band 102 d from becoming damaged,dislodged, etc. by external debris.

The flexible member 102 may provide one or more functions. For example,the flexible member 102 may provide a means of assembling the fiberoptic cable 50 inside the cable chain 34 with a predetermined amount ofslack. For example, as shown in FIG. 5, the fiber optic cable 50 may beforced by the flexible members 102 into a “sine wave” to “snake” aboutthe neutral axis of the cable chain 34 around the flexible members 102.The fiber optic cable 50 is assembled in the manner over the entirelength of the cable chain 34. FIG. 5 shows a peak-to-valley of the fiberoptic cable 50 assembled in this manner over three chain links 54 a, 54b, 54 c. This frequency can easily be adjusted depending on differentrequirements in the system 10 as each chain link 54 will be able toaccept and retain a flexible member 102. Adequate slack in the fiberoptic cable 50 accommodates the stretching of the cable chain 34 as itis subject to tension from the shearer 18.

The flexible member 102 may provide a buffer, or cushion, when the fiberoptic cable 50 is subject to tension. When the fiber optic cable 50 issubject to tension, the resilient property of the flexible member 102will allow the “snaked” cable 50 to compress the material and deflectinwardly (see FIG. 6), providing a means to limit over-tension andpremature failure of the fiber optic cable 50. The flexible member 102may fill a void in the first compartment 94 that could otherwise beoccupied by debris (which may accelerate wear or cause failure of thefiber optic cable 50).

Various independent features and independent advantages of the inventionmay be set forth in the following claims.

What is claimed is:
 1. A chain link assembly for a cable chain assemblyin a mining machine, the cable chain assembly extending along an axis,the chain link assembly comprising: a chain link having a plurality ofwalls cooperating to define a compartment opening in the direction ofthe axis, a centerline being defined between the plurality of walls andextending parallel to the axis, the chain link including a firstprojection and a second projection extending opposite the firstprojection, the chain link defining a length measured between the firstprojection and the second projection and parallel to the direction ofthe axis, a fiber optic cable being supportable in the compartment, aservice line being supportable in the compartment; and a flexible membersupported in the compartment and engageable with the fiber optic cable,the flexible member having a length that is shorter than the lengthbetween the first projection and the second projection, the flexiblemember positioning the fiber optic cable toward one of the plurality ofwalls and away from the centerline at least when the fiber optic cableis in a slack state.
 2. The chain link assembly of claim 1, wherein theflexible member includes a compressible member supported on another ofthe plurality of walls opposite the one wall toward which the fiberoptic cable is biased.
 3. The chain link assembly of claim 2, whereinthe compressible member includes a hollow member having a first portionengageable with the fiber optic cable and a second portion engaging theopposite one of the plurality of walls.
 4. The chain link assembly ofclaim 3, wherein the hollow member has a substantially tubular crosssection.
 5. The chain link assembly of claim 1, wherein the chain linkfurther includes an internal wall dividing the compartment into a firstcompartment and a second compartment, the fiber optic cable beingsupportable in the first compartment, the service line being supportablein the second compartment.
 6. The chain link assembly of claim 5,wherein the internal wall is formed with the one of the plurality ofwalls and an opposite one of the plurality of walls.
 7. The chain linkassembly of claim 5, wherein the internal wall is separate from andconnected to the one of the plurality of walls and an opposite one ofthe plurality of walls.
 8. The chain link assembly of claim 1, whereinthe flexible member has a surface engageable with the fiber optic cable,the surface including a low friction material.
 9. The chain linkassembly of claim 8, wherein the surface is coated with the low frictionmaterial.
 10. A chain link assembly for a cable chain assembly in amining machine, the cable chain assembly extending along an axis, thechain link assembly comprising: a chain link having a plurality of wallscooperating to define a compartment opening in the direction of theaxis, the chain link including a first projection and a secondprojection extending opposite the first projection, the chain linkdefining a length measured between the first projection and the secondprojection and parallel to the direction of the axis, a fiber opticcable being supportable in the compartment, a service line beingsupportable in the compartment; and a flexible member supported in thecompartment and engageable with the fiber optic cable, the flexiblemember having a length that is shorter than the length between the firstprojection and the second projection, the flexible member positioningthe fiber optic cable toward one of the plurality of walls, wherein thechain link further includes an internal wall dividing the compartmentinto a first compartment and a second compartment, the fiber optic cablebeing supportable in the first compartment, the service line beingsupportable in the second compartment, wherein the internal wallincludes a connector, a portion of the flexible member being capturedbetween the connector and an opposite one of the plurality of walls. 11.The chain link assembly of claim 10, wherein the flexible memberincludes a compressible member supported on another of the plurality ofwalls opposite the one wall toward which the fiber optic cable isbiased.
 12. The chain link assembly of claim 11, wherein thecompressible member includes a hollow member having a first portionengageable with the fiber optic cable and a second portion engaging theopposite one of the plurality of walls.
 13. The chain link assembly ofclaim 12, wherein the hollow member has a substantially tubular crosssection.
 14. The chain link assembly of claim 10, wherein the internalwall is formed with the one of the plurality of walls and an oppositeone of the plurality of walls.
 15. The chain link assembly of claim 10,wherein the internal wall is separate from and connected to the one ofthe plurality of walls and an opposite one of the plurality of walls.16. The chain link assembly of claim 10, wherein the flexible member hasa surface engageable with the fiber optic cable, the surface including alow friction material.
 17. A cable chain assembly for a mining machine,the cable chain assembly extending along an axis, the assemblycomprising: a plurality of chain links each having a top wall, a bottomwall, and at least one side wall cooperating to define a compartmentopening in the direction of the axis; a fiber optic cable extendingthrough the compartment in each of the plurality of chain links, thefiber optic cable extending generally along a wave-shaped path relativeto the plurality of chain links; a service line supportable in thecompartment in each of the plurality of chain links; a first membersupported in the compartment of one of the plurality of chain links andengageable with the fiber optic cable, the first member positioning thefiber optic cable toward one of the walls of the one of the plurality ofchain links; and a second member supported in the compartment of asecond one of the plurality of chain links and engageable with the fiberoptic cable, the second member positioning the fiber optic cable towardone of the walls of the second one of the plurality of chain links;wherein the first member and the second member cooperate to position thefiber optic cable along at least a portion of the wave-shaped path. 18.The cable chain assembly of claim 17, wherein at least one of the firstmember and the second member is flexible.
 19. The cable chain assemblyof claim 18, wherein each of the first member and the second memberincludes a compressible member supported on an opposite one of the firstplurality of walls.
 20. The cable chain assembly of claim 19, whereinthe compressible member includes a hollow member having a first portionengaging the fiber optic cable and a second portion engaging theopposite one of the first plurality of walls.
 21. The cable chainassembly of claim 17, wherein a third one of the plurality of chainlinks is connected between the one of the plurality of chain links andthe second one of the plurality of chain links, the third one of theplurality of chain links not having a member in the compartment.
 22. Thecable chain assembly of claim 17, wherein each of the plurality of chainlinks further include an internal wall dividing the compartment into afirst compartment and a second compartment, the fiber optic cable beingsupported in the first compartment, the service line being supported inthe second compartment.
 23. The cable chain assembly of claim 17,wherein the first member has a surface engageable with the fiber opticcable, the surface including a low friction material.
 24. A chain linkassembly for a cable chain assembly in a mining machine, the cable chainassembly extending along an axis, the chain link assembly comprising: achain link having a first wall, a second wall opposite the first wall,and a third wall extending between the first wall and the second wall,the first wall, second wall, and third wall cooperating to define acompartment opening in the direction of the axis, a centerline definedbetween the first wall, second wall, and third wall and extendingparallel to the axis; a fiber optic cable supportable in thecompartment; a service line supportable in the compartment; a connectorcoupled to the third wall; and a resilient member supported by theconnector and engageable with the fiber optic cable, the resilientmember having a portion engageable with the fiber optic cable, theresilient member positioning the fiber optic cable toward one of thefirst wall and the second wall and away from the centerline at leastwhen the fiber optic cable is in a slack state.
 25. The chain linkassembly of claim 24, wherein the resilient member is hollow and has asubstantially tubular cross section.
 26. The chain link assembly ofclaim 24, wherein another portion of the resilient member is capturedbetween the connector and the other of the first wall and the secondwall.
 27. The chain link assembly of claim 24, wherein the third wallincludes an internal wall dividing the compartment into a firstcompartment portion and a second compartment portion, the fiber opticcable being supportable in the first compartment portion, the serviceline being supportable in the second compartment portion.
 28. The chainlink assembly of claim 24, wherein the portion of the resilient memberhas a surface engageable with the fiber optic cable, the surfaceincluding a low friction material.
 29. The chain link assembly of claim24, wherein the chain link includes a first lug for coupling the chainlink to an adjacent chain link and a second lug for coupling the chainlink to another adjacent chain link, the chain link defining a lengthmeasured between the first lug and the second lug and parallel to thedirection of the axis, and wherein the resilient member has a lengththat is shorter than the length between the first lug and the secondlug.